The design of displays for computing devices is always a compromise. If the display is large, then the device is too expensive, and too large, to be practical. If the display is small, then too little information can be displayed at once. Thus, when viewing large documents, users can only view a small portion at any one time, and must often manipulate controls to adjust the visible portion—looking first at one part, then at another. This works, but is inefficient.
Printed documents are easier to read than most computer displays. They can be much larger and have higher resolution than computer displays. They can also be navigated quickly—for example, a salesperson familiar with the company catalogue can very quickly locate the page where an item of interest is described. However, printed documents have the disadvantage that they are static, and often out-of-date.
One way of interacting with a printed paper is described by Anoto AB, a subsidiary of C Technologies AB of Sweden. They print special paper forms, which have a specific address printed in each 2 mm×2 mm square section. The Anoto™ system uses a pen with a built-in camera that recognizes the printed pattern. If a user writes on the paper with this pen, the pen reads the addressing information, and sends the addresses to a server. The server forwards the pen's recorded motion to the entity that has leased/purchased the identified portion of the fixed address space. For example, suppose Filofax Group Limited purchases a section of the address space for e-mail purposes. A user could then buy e-mail paper from Filofax®. When the user writes on the e-mail paper and checks the “send” box, the pen sends its recorded movements (a list of the addresses on the page over which it passed) to the Anoto™ server. The server looks up the addresses, sees that they were leased to Filofax, and forwards the recorded movements to that company's server. The Filofax server then translates the pen's motion into an electronic message, e.g., e-mail, and then e-mails it to the user.
A disadvantage of the Anoto™ system is that the encoded address is of a fixed size. Each location on one of their printed pages corresponds to an absolute location in a 60 million km2 grid. This works well for printed forms (where a small section of the address can be repeatedly used on thousands of identically-printed documents), but it doesn't allow for user-printed documents. Further, the Anoto™ system patterns must be printed on a high resolution printer at approximately 1000 dpi to fit the whole address into a 2 mm×2 mm square. Also, the system uses the combination of pen/printed paper only as an input device, and the method they employ can only provide positional information while the pen can see the paper. It does not provide a means to display up-to-date information to the user, and if you slide off the edge of the page, it stops working.
Several mechanisms are presently available for encoding an address on printed media that identifies the printed document or points to an address, i.e., Uniform Resource Identifier (URI). For example, one could print a barcode, or other identifying mark, on the document. Then one could read the barcode, recall the document, and then explore it using a pointing device (such as a mouse).
One can also use printed bar codes to serve as input devices. For example, in a store, the clerk can scan a printed bar code, rather than having to manually type an item number. It is even possible to encode large amounts of information in printed marks, and then extract it by scanning. Examples include the dataglyph developed by Xerox Corporation, and the digital watermark system developed by Digimark.
While there are numerous devices and methods for interacting with printed documents, there is a need for devices and mechanisms which allow the printed document to replace both large keyboards, and large display devices, in a very natural way.